A fish shape appeared on Paumanok on Friday morning, carried in on high tide. A dolphin: It had started from the sea and made its way into Brooklyn from without, working along the wood and concrete embankments toward the river head, and by mid-morning it was paused by one of Gowanus's empty lots, surfacing and plunging out of and in to the mucoid black. A gathering crowd of locals and police watched it from the shore; it was hyperventilating and bleeding from its fin. Biologists from the Riverhead Foundation arrived. The next high tide wouldn't be until 7 p.m.

Snow began to fall. At 5:30 it found itself breached on concrete piling, wedged next to a rock under the Union bridge, and stopped moving. "Myself & an ecologist were there at the moment the dolphin died. He cried out," Aaron Stewart-Ahn wrote. "Police put up tape."

"Fish-shape Paumanok" is what Walt Whitman called Long Island, borrowing a Native American name. It was, he wrote in "Starting from Paumanok," "where I was born/Well-begotten, and rais'd by a perfect mother." Nine years after he wrote those words, a small waterway, located in a tidal inlet at the far west side of Long Island in the city of Brooklyn, was dredged and deepened and turned into a canal. It was up this canal that the brownstone that built Park Slope and Carroll Gardens was carried, and around it that Brooklyn's industry thrived: factories, warehouses, refineries, all using the canal as both a thoroughfare and a dump site. Within a half-century, Brooklyn had become a borough and Gowanus had become "almost solid" — filled with thick coal tar and sewage, and infested with microbes.

The sewage and microbes and filth and disease in the canal prevented quicker action when the dolphin was found, but it was likely doomed anyway, weak and bleeding, unable to find its way out of the sick and milky cul-de-sac. Gowanus itself is maybe not so doomed. In the 100 years since, it has gotten cleaner, then less clean, then more clean; Brooklyn has got safer, then less safe, then more safe; richer, then less rich, then more rich.

Still, some things never change. In 2007, a whale found its way up the canal and spent two days swimming before dying in the water; 55 years before that, a shark entered the Gowanus and was shot by the police.

Sixty years before the shark, 115 years before the whale, 120 years before the dolphin, Walt Whitman lay dying, his lungs infected and filled with a viscous fluid. He was in Camden, maybe 120 miles from where he started on fish-shaped Paumanock.

We'll probably never know where the dolphin was born, or how far it swam before it died. Very few of us really ever get that far from where we start. Many of us spend our lives mistakenly struggling through syrup and tar, directionless, weak, terrified, mutely appealing to unrecognizable shoredwellers. But some can still reach the open sea. Whitman had completed, the year before, a final edition of Leaves of Grass, in which "Starting from Paumanok" appears. "Was somebody asking to see the soul?" the poem asks.

See, your own shape and countenance, persons, substances, beasts,
the trees, the running rivers, the rocks and sands.

All hold spiritual joys and afterwards loosen them;
How can the real body ever die and be buried?